README.md in lograge-sql-0.2.0 vs README.md in lograge-sql-0.3.0

@@ -20,9 +20,47 @@
 ```ruby
 # config/initializers/lograge
 require 'lograge/sql/extension'
 ```
 
+## Customization
+
+By default, the format is a string concatenation of the query name, the query duration and the query itself joined by `\n` newline:
+
+```
+method=GET path=/mypath format=html ...
+Object Load (0.42) SELECT "objects.*" FROM "objects"
+Associations Load (0.42) SELECT "associations.*" FROM "associations" WHERE "associations"."object_id" = "$1"
+```
+
+However, having `Lograge::Formatters::Json.new`, the relevant output is 
+
+```json
+{
+    "sql_queries": "name1 ({duration1}) {query1}\nname2 ({duration2}) query2 ...",
+    "sql_queries_count": 3
+}
+```
+
+To customize the output:
+
+```ruby
+# config/initializers/lograge.rb
+Rails.application.configure do
+
+  # Instead of extracting event as Strings, extract as Hash. You can also extract
+  # additional fields to add to the formatter
+  config.lograge_sql.extract_event = Proc.new do |event|
+    { name: event.payload[:name], duration: event.duration.to_f.round(2), sql: event.payload[:sql] }
+  end
+  # Format the array of extracted events
+  config.lograge_sql.formatter = Proc.new do |sql_queries|
+    sql_queries
+  end
+end
+```
+
+
 ## Contributing
 
 Bug reports and pull requests are welcome on GitHub at https://github.com/iMacTia/lograge-sql.